fuel filter question

[SLAY]

Greeting, I should know better but here goes: Several days ago in preperation for a road trip I decided to replace my fuel filter, Armed with a quality filter from the local cummins dealer I noticed the kit had two O rings a large and a smaller square cut type.



Well in my infinite wisdom I figured out where the larger one went and at the time rationlized the smaller one must have been for another application, this was further reinforced when I inspected the old filter after removeal. A 1000 miles away from home a light goes off in my head and it seams obvious where this other O ring should fit. I'm assuming that the original filter's smaller o ring remained on the mounting shaft, but I'm not absolutely sure it even had one? Thinking about it I 'm not sure what the purpose of this small O ring serves?



Either way I will probally change filter again just to keep my sanity.



Anyone know what that little O ring is for? I'm sure they put one there for a reason ...



thanks



Steve

 

[Withers]

The smaller ring is for the mounting shaft that the filter threads on to. When you pull the old filter off, be sure to either pull the old ring off or leave it on, but don't put a new one on, unless you have taken the old one off, or else you will start stacking one ring on another and once you have enough stacked on top of each other the filter won't seat properly, and could leak or maybe suck air,

 

[Titan]

The smaller squared one does go on the mounting shaft but the other one goes on the fuel filter drain and water sensor assembly. If the old O-ring on the drain and sensor assembly wasn't in bad shape you will be fine without replacing it. However, if you didn't remove the small squared O-ring from the mounting shaft you could have a air or fuel leak. Watch it... If no leak is present, then you have a tight seal. Good luck.

 

[SLAY]

No leaks that I see, since this filter is similar in constrution to the typical oil filter, the outer canister sealing ring is obvious as well as the drain O-ring just not sure what the inner shaft ring accomplishes? I'm not sure that its is for air since I would think that the fuel filter onced primed would has no way for air to be at that part of the system unless I ran my tank dry.



Well I guess if thats my only problem I have none!



thanks



Steve

 

[Titan]

Without a lot of thought, I always assumed that the inner O-ring prevented the mixing of filtered and unfiltered fuel. Because I was not positive I asked my father who works for Cummins Northwest and he verified my hunch. Without this O-ring fuel will mix.